Introduction to Oncology: Pathophysiology, Screening, Staging, and Treatment Modalities

Historical Context and Strategic Initiatives in Oncology

• Early Historical Origins of Oncology:

  • The oldest known written description of cancer dates back to ancient Egypt in approximately 3000 BC, detailing breast cancer treatments.
  • Hippocrates (460–370 BC) originated the term cancer, deriving it from the Greek word for crab (karkinos), later translated into the Latin cancer by Celsus (25 BC – 50 AD) due to the crab-like appearance of solid tumors with extended blood vessels.
  • Renaissance Era (16th–18th Centuries): Marked by advances in autopsies, initial techniques for tumor resection, formal documentation of metastasis, and the early introduction of anesthesia.
  • 19th Century: Discovery of cell biology and early applications of radiation. During this period, a diagnosis of cancer carried significant social taboo.
  • 20th Century Administrative Milestones:
  • 1913: Establishment of the American Cancer Society (ACS).
  • 1937: Enactment of the National Cancer Act of 1937, establishing the National Cancer Institute (NCI) as an independent research institution.

• The National Cancer Act of 1971 ("War on Cancer"):

  • Signed into law by President Richard Nixon, heavily influenced by Mary Lasker (philanthropist and chairwoman of the ACS board), who called for a national "moonshot for cancer."
  • Lasker highlighted federal underfunding, famously noting that less money was spent on cancer research than on chewing gum.
  • Allocated $1.6\text{ billion}$ over three years (equivalent to approximately $11\text{ billion}$ today) to support basic cellular research and clinical trial networks.
  • At the time of passage, cancer was the second leading cause of death in the United States — a rank it still holds today.
  • Systematic drops in overall cancer incidence, morbidity, and mortality began to manifest in the 1990s as a direct result of research investments and tobacco control.

• Modern Cancer Moonshot Initiatives:
  • 2016 Launch: Launched under the Obama-Biden administration with three core operational pillars:
  1. Accelerate scientific discovery in cancer biology and therapeutics.
  2. Foster greater inter-institutional collaboration.
  3. Improve comprehensive medical and genomic data sharing.
  • 2022 Reignited Goals:
  • Reduce the national age-adjusted cancer mortality rate by at least $50\%$ over the next 25 years.
  • Substantially improve the living and survival experience for cancer patients and their families.
  • Funding Mechanisms and Federal Budgetary Status:
  • Funded initially via the 21st Century Cures Act (December 2018), allocating $1.8\text{ billion}$ across 7 fiscal years.
  • Approximately $7\text{ billion}$ of the National Institutes of Health's (NIH) total $47\text{ billion}$ annual budget is appropriated directly for cancer research.
  • Recent budget adjustments included a $2.7\text{ billion}$ spending cut to the National Cancer Institute, creating ongoing uncertainty regarding future initiative timelines.

Pathophysiology, Carcinogenesis, and Genetics

• Fundamental Definition of Cancer:
  • Cancer represents a vast collection of over 100 distinct diseases characterized fundamentally by uncontrolled, abnormal cell division and metabolic dysregulation.

• Distinguishing Hallmarks of Cancer Cells vs. Normal Cells:
  • Unchecked Proliferation: Insensitivity to anti-growth signals and constitutive activation of division pathways.
  • Evasion of Apoptosis: Failure to undergo programmed cell death despite massive DNA damage or structural aberrations.
  • Invasiveness: Uninhibited growth through basement membranes and adjacent non-native tissue boundaries.
  • Angiogenesis: Tumor-driven recruitment and growth of new blood vessel networks (via factors like VEGF) to supply oxygen and nutrients.
  • Immune Evasion: Active suppression or disguise mechanisms that prevent recognition and destruction by cytotoxic T cells and natural killer (NK) cells.
  • Genomic Instability: Progressive accumulation of chromosomal aberrations, gene duplications, deletions, and point mutations.

• Cell Cycle Control and Genetic Mechanisms:
  • Cellular progression is regulated through distinct checkpoints ($G_1/S$, $G_2/M$, and Spindle Assembly checkpoints).

• Proto-Oncogenes to Oncogenes:

  • Proto-oncogenes encode normal proteins that promote physiological cell growth, division, and survival.
  • Gain-of-function mutations transform proto-oncogenes into oncogenes, resulting in constitutively active proteins that continuously drive proliferation.
  • Examples: HER2/neu (receptor tyrosine kinase in breast/gastric cancers), KRAS (GTPase involved in intracellular signaling cascades across colon, lung, and pancreatic carcinomas).

• Tumor Suppressor Genes:

  • Genes that normally function as dynamic "brakes" on cell division, DNA repair facilitators, or triggers for apoptosis.

  • Inactivation or loss-of-function mutations eliminate these regulatory safeguards, permitting unchecked expansion of mutated daughter cells.

  • Examples: BRCA1 and BRCA2 (DNA double-strand break repair), p53 (the "guardian of the genome," controlling cell cycle arrest at $G_1/S$ and apoptotic signaling).

  • Multi-Step Carcinogenesis and the Two-Hit Model:

• Carcinogenesis is a multi-step process accumulating over time: initial inactivation of a tumor suppressor gene, localized proliferation, inactivation of DNA repair genes, conversion of proto-oncogenes to oncogenes, and eventual genetic instability leading to invasive and metastatic disease.

• Knudson's Two-Hit Model (1971):
  • Formulated by Alfred Knudson through studies on pediatric retinoblastoma.
  • Postulates that both alleles of a tumor suppressor gene must be inactivated to initiate oncogenesis.
  • In sporadic cancers, two distinct somatic mutation events ("hits") must occur within the same cell lineage.
  • In hereditary cancers, one mutated allele is inherited through the germline (first hit), requiring only a single additional somatic mutation (second hit) in any tissue cell to trigger disease.

Cellular Alterations, Terminology, and Metastasis

• Non-Cancerous Cellular Responses:
  • Hypertrophy: Increase in individual cell size without an increase in overall cell number (e.g., physiological response of skeletal muscle to resistance training or pathological left ventricular hypertrophy in response to chronic hypertension).
  • Hyperplasia: Rapid multiplication of morphologically normal cells resulting in organ or tissue enlargement (e.g., Benign Prostatic Hyperplasia [BPH] or endometrial hyperplasia under unopposed estrogen).
  • Dysplasia: Advanced disordered growth and maturation of an epithelium, characterized by loss of cellular uniformity and architectural orientation. Cells exhibit nuclear atypia and hyperchromasia. Dysplastic changes are non-invasive but carry a high risk of malignant transformation (e.g., a dysplastic nevus evolving into cutaneous melanoma).

• Major Taxonomic Classifications of Malignancies:

  • Carcinoma: Malignancies arising from epithelial cells lining external and internal body surfaces, glands, and organs ($>80\%$ of all human cancers).
  • Sarcoma: Malignancies arising from mesenchymal stem cell derivatives, including bone, cartilage, fat, smooth muscle, skeletal muscle, and blood vessels.
  • Central Nervous System Malignancies: Primary cancers originating within the parenchyma of the brain or spinal cord (e.g., gliomas, glioblastomas, astrocytomas).
  • Leukemia: Hematologic cancers originating in the hematopoietic stem cells of the bone marrow, circulating predominantly in the bloodstream.
  • Lymphoma and Myeloma: Malignancies of the lymphatic system and immune cells; lymphomas arise in lymph nodes/lymphoid tissues (T cells, B cells, NK cells), while myelomas derive from antibody-producing plasma cells in the bone marrow.

• Distinction Between Benign and Malignant Neoplasms:

  • Benign: Slow growth rate; non-invasive growth with well-circumscribed or encapsulated margins; low potential for structural destruction; low overall mortality risk (dependent on location, such as intracranial space); named using the suffix -oma (e.g., Adenoma, Osteoma, Squamous cell papilloma).
  • Malignant: Rapid growth rate; locally invasive, infiltrating surrounding tissue structures without clear borders; high capacity for distant metastasis; substantial mortality risk; named using suffixes -carcinoma or -sarcoma (e.g., Adenocarcinoma, Osteosarcoma, Squamous cell carcinoma).

• Anatomic and Histologic Prefixes:

  • adeno-: Glandular tissue
  • chondro-: Cartilage
  • erythro-: Red blood cell
  • hemangio-: Blood vessel tissue
  • hepato-: Liver
  • lipo-: Adipose/fat tissue
  • lympho-: Lymphocyte/lymphoid tissue
  • melano-: Pigment-producing cell (melanocyte)
  • myelo-: Bone marrow elements
  • myo-: Muscle tissue
  • osteo-: Bone tissue

• Pathophysiology of Metastasis:
  • Metastasis describes the cascade by which malignant cells detach from the primary tumor, invade localized tissues, penetrate fluid transport systems, and colonize distant organs.

• Sequential Steps in the Metastatic Cascade:
  1. Local Invasion & Detachment: Cancer cells downregulate cell-adhesion molecules (e.g., E-cadherin) and secrete matrix metalloproteinases (MMPs) to digest extracellular matrix (ECM) components.
  2. Intravasation: Invasion through basement membranes into adjacent capillary blood vessels or lymphatic channels.
  3. Circulation Survival: Tumor cells circulate as single cells or emboli, surviving shear stress and immune surveillance.
  4. Extravasation: Adherence to endothelial walls of distant capillary beds, followed by migration into tissue parenchyma.
  5. Metastatic Outgrowth & Angiogenesis: Secretion of growth factors to induce neovascularization and establish secondary secondary tumors.
• Nomenclature Rule: Metastatic disease is always named and classified according to its primary cell origin (e.g., colon cancer that spreads to the liver is designated as "metastatic colon cancer to the liver," not liver cancer).

Epidemiology and Statistical Data

• General National Burden and Costs (United States):

  • Cancer is the second leading cause of mortality overall in the US, accounting for approximately 1 in every 5 deaths (the leading cause of death is cardiovascular disease).
  • Annual direct medical expenditures for cancer care reached $140.7\text{ billion}$ in 2019.

• Pediatric Oncology Epidemiology:

  • Cancer is the second leading cause of mortality in pediatric patients aged 1–14 years (unintentional injury/accidents is #1).
  • Modern 5-year survival rates across all pediatric cancers average $85\%$ (a substantial rise from $58\%$ recorded in the mid-1970s).
  • Distribution of Common Pediatric Cancers:
  • Leukemias: $26\%$
  • Central Nervous System (CNS) Tumors: $26\%$
  • Lymphomas: Remaining majority portion
  • Nebraska Regional Data: Pediatric brain cancer is the leading cause of pediatric cancer diagnosis within the state of Nebraska.

• 2022 US Projected Cancer Incidence and Mortality Breakdown:

  • Estimated New Cases (2022):

  • Males Total: $983,160$

    • Prostate: $268,490$ ($27\%$
    • Lung & bronchus: $117,910$ ($12\%$
    • Colon & rectum: $80,690$ ($8\%$
    • Urinary bladder: $61,700$ ($6\%$
    • Melanoma of the skin: $57,180$ ($6\%$
    • Kidney & renal pelvis: $50,290$ ($5\%$
    • Non-Hodgkin lymphoma: $44,120$ ($4\%$
    • Oral cavity & pharynx: $38,700$ ($4\%$
    • Leukemia: $35,810$ ($4\%$
    • Pancreas: $32,970$ ($3\%$

  • Females Total: $934,870$

    • Breast: $287,850$ ($31\%$
    • Lung & bronchus: $118,830$ ($13\%$
    • Colon & rectum: $70,340$ ($8\%$
    • Uterine corpus: $65,950$ ($7\%$
    • Melanoma of the skin: $42,600$ ($5\%$
    • Non-Hodgkin lymphoma: $36,350$ ($4\%$
    • Thyroid: $31,940$ ($3\%$
    • Pancreas: $29,240$ ($3\%$
    • Kidney & renal pelvis: $28,710$ ($3\%$
    • Leukemia: $24,840$ ($3\%$

  • Estimated Deaths (2022):

  • Males Total: $322,090$

    • Lung & bronchus: $68,820$ ($21\%$
    • Prostate: $34,500$ ($11\%$
    • Colon & rectum: $28,400$ ($9\%$
    • Pancreas: $25,970$ ($8\%$
    • Liver & intrahepatic bile duct: $20,420$ ($6\%$
    • Leukemia: $14,020$ ($4\%$
    • Esophagus: $13,250$ ($4\%$
    • Urinary bladder: $12,120$ ($4\%$
    • Non-Hodgkin lymphoma: $11,700$ ($4\%$
    • Brain & other nervous system: $10,710$ ($3\%$

  • Females Total: $287,270$

    • Lung & bronchus: $61,360$ ($21\%$
    • Breast: $43,250$ ($15\%$
    • Colon & rectum: $24,180$ ($8\%$
    • Pancreas: $23,860$ ($8\%$
    • Ovary: $12,810$ ($4\%$
    • Uterine corpus: $12,550$ ($4\%$
    • Liver & intrahepatic bile duct: $10,100$ ($4\%$
    • Leukemia: $9,980$ ($3\%$
    • Non-Hodgkin lymphoma: $8,550$ ($3\%$
    • Brain & other nervous system: $7,570$ ($3\%$

Risk Factors and Etiology

• Overview of Modifiable vs. Non-Modifiable Etiologies:

  • According to 2024 American Cancer Society epidemiological data, nearly $40\%$ of all cancer cases diagnosed in adults over age 30 are attributable to potentially modifiable risk factors.

• Modifiable Environmental and Behavioral Risk Factors:

  • Tobacco Use & Secondhand Smoke:
  • Inhaled smoke (linked to lung cancer) and smokeless/chewing products (linked to oral, esophageal, and pancreatic cancers).
  • Directly implicated in $30\%$ of all cancer deaths nationwide; single largest preventable cause of cancer death.
  • $85\%\text{--}90\%$ of all primary lung cancers occur directly in current or former tobacco users.
  • Contains over 250 verified carcinogenic chemicals (e.g., nitrosamines, polycyclic aromatic hydrocarbons).
  • Physiological Timeline of Quitting Benefits:
    • Immediate normalization of blood pressure and heart rate.
    • Carbon monoxide ($CO$) blood levels decline to normal within days.
    • Reduced coughing and phlegm production within weeks.
    • Improvement in gustatory and olfactory acuity within weeks.
    • Measurable improvements in overall forced expiratory lung function within months.

• Ethanol / Alcohol Consumption:
  • Dose-dependent risk elevation for cancers of the oral cavity, pharynx, larynx, esophagus, liver, colon, rectum, and female breast.
  • Risk scales with volume consumed; no solid medical evidence supports the concept that red wine protects against cancer.
  • AICR Guidelines: Complete avoidance recommended. If consumed, daily intake should not exceed $≤ 2$ standard drinks for men and $≤ 1$ standard drink for women.
  • Standard Drink Equivalents ($14\text{ grams}$ pure alcohol):
    • $12\,\text{fl oz}$ of regular beer ($\sim 5\%$ alcohol content).
    • $8\text{--}9\,\text{fl oz}$ of malt liquor ($\sim 7\%$ alcohol content).
    • $5\,\text{fl oz}$ of table wine ($\sim 12\%$ alcohol content).
    • $1.5\,\text{fl oz}$ shot of 80-proof distilled spirits ($\sim 40\%$ alcohol content).

• Dietary Factors:
  • High consumption of charred meats, red meats, and sodium-nitrate processed meats increases risk.
  • Low intake of plant dietary fiber, calcium, fruit, and fresh vegetables increases colorectal cancer risks. High Calcium and Vitamin D intake are under study for colorectal protective mechanisms.
• Obesity and Overweight:
  • Etiologically linked to 13 distinct adult cancers: Meningioma, Adenocarcinoma of the esophagus, Multiple myeloma, Kidney, Uterus, Ovary, Thyroid, Post-menopausal breast, Liver, Gallbladder, Upper stomach, Pancreas, and Colon/Rectum.

• Exogenous Hormones:

  • Estrogen Replacement Therapy / Hormone Replacement Therapy (HRT) raises risks for breast and endometrial cancer (estrogen-only therapy carries lower breast risk compared to combined estrogen-progestin therapy).

• Ionizing Radiation Exposure:

  • Causes direct DNA single- and double-strand breaks. Sources include medical X-rays, gamma rays, CT/PET scans, and radon gas.
  • Lifetime radiation exposure is cumulative. Medical imaging protocols require careful dose monitoring, particularly in pediatric populations.
  • Environmental nuclear fallout (e.g., Nevada/Pacific atmospheric testing between 1945–1963) dispersed Iodine-131 ($^{131}\text{I}$) across Utah, Colorado, Idaho, Nevada, and Montana. Children who consumed milk contaminated with fallout exhibited significantly higher rates of primary thyroid cancer.

• Ultraviolet (UV) Radiation and Sun Exposure:

  • Both UVA (aging, deep penetration) and UVB (burning, superficial) cause cumulative DNA photoproduct damage (thymine dimers) mutating tumor suppressor genes.

  • Association with Basal Cell Carcinoma established in 1927; Squamous Cell Carcinoma in 1955. Severe, blistering sunburns during childhood strongly correlate with cutaneous Melanoma development.

  • 1 in 5 Americans develop skin cancer by age 70. Sustaining 5 or more severe blistering sunburns during lifetime doubles overall Melanoma risk. Indoor tanning beds emit $10\times\text{--}15\times$ higher UV radiation concentrations than peak midday natural sunlight.

  • Non-Modifiable Risk Factors:

• Age: The strongest single non-modifiable risk factor for cancer. Cancer incidence rates exhibit an exponential climb past age 50, peaking in the 80–84 age demographic ($>2300\text{ cases per }100,000\text{ persons}$).

• Hereditary Cancer Syndromes:

  • The vast majority ($85\%\text{--}90\%$

  • Over 50 inherited cancer predisposition genes identified:

    • BRCA1 / BRCA2 mutations: Breast, ovarian, pancreatic, and prostate cancers.
    • Lynch Syndrome (Hereditary Non-Polyposis Colorectal Cancer - HNPCC): DNA mismatch repair (MMR) gene mutations driving colorectal, endometrial, ovarian, gastric, pancreatic, and renal pelvic cancers.
    • Li-Fraumeni Syndrome: Germline p53 gene mutations resulting in early-onset sarcomas, leukemias, brain tumors, and adrenocortical carcinomas.
    • Familial Melanoma: Mutations in CDKN2A (p16).

  • Other Risk Factors (Carcinogens, Inflammation, Infection):

• Carcinogenic Agents: 62 designated primary human carcinogens, including occupational exposures (asbestos, coal tar) and environmental toxins.

• Radon Exposure: Soil decay product of uranium. Radon gas is a major cause of lung cancer in non-smokers. In Nebraska, approximately half ($50\%$

• Chronic Inflammation: Chronic cell damage and repair cycles increase DNA copy errors. Conditions like Ulcerative Colitis and Crohn's disease carry increased risks for colorectal adenocarcinoma.

• Immunosuppression: Organ transplant recipients taking immunosuppressants and individuals living with HIV show elevated rates of virus-driven malignancies due to impaired immune surveillance.

• Oncogenic Infectious Agents:

  • Epstein-Barr Virus (EBV): Burkitt lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma.
  • Hepatitis B Virus (HBV) & Hepatitis C Virus (HCV): Hepatocellular carcinoma.
  • Human Papillomavirus (HPV) (High-risk strains 16, 18): Cervical, anal, penile, vaginal, vulvar, and oropharyngeal carcinomas.
  • HPV-8: Kaposi sarcoma (in conjunction with HHV-8).
  • Helicobacter pylori: Noncardia gastric adenocarcinoma and MALT (Mucosa-Associated Lymphoid Tissue) lymphoma.
  • Human T-cell Lymphotropic Virus-1 (HTLV-1): Adult T-cell leukemia/lymphoma.
  • Merkel Cell Polyomavirus: Merkel cell carcinoma.
  • Helminthic Parasites (Schistosoma haematobium, Clonorchis sinensis): Bladder carcinoma and cholangiocarcinoma.

Clinical Manifestations and Screening Guidelines

• General Physical Manifestations ("Signs" of Cancer):

  • Constitutional Symptoms: Unexplained fevers, rapid involuntary weight loss ($>10\%$ body weight), profound fatigue.
  • Symptom Complex: Persistent nausea/vomiting, severe drenching night sweats, generalized lymphadenopathy.
  • Gastrointestinal & Pain Markers: Early satiety (feeling full rapidly when eating), unexplained visceral or localized pain (persistent headaches, severe abdominal pain), pain that wakes a patient from sleep at night.
  • Hematologic & Tissue Signs: Unexplained bruising or bleeding (petechiae, ecchymosis, epistaxis, hematuria, hematochezia), persistent changes in bowel or bladder habits without underlying cause.

• American Cancer Society Screening Guidelines for Average-Risk Asymptomatic Individuals:

  • Breast Cancer:
  • Women 40–44: Choice to initiate annual mammography screening.
  • Women 45–54: Mandatory annual screening mammography recommended.
  • Women 55+: Transition to biennial (every 2 years) screening, or maintain optional annual screening. Continue as long as health status is good and life expectancy is $≥ 10\text{ years}$.
  • Cervical Cancer:
  • Women 25–65: Primary HPV DNA test every 5 years (preferred method); or Pap test combined with HPV DNA co-testing every 5 years; or Pap test alone every 3 years.
  • Women >65: Discontinue screening if regular negative screening history over the preceding 10 years (with most recent test within past 5 years).
  • Women with Total Hysterectomy: Discontinue screening completely unless surgery was performed as treatment for CIN 2/CIN 3 or cervical cancer in the past 25 years.
  • Colorectal Cancer:
  • Adults 45+: High-sensitivity guaiac-based fecal occult blood test (gFOBT) or fecal immunochemical test (FIT) annually; OR Multi-target stool DNA (fit-fecal) test every 3 years; OR Flexible sigmoidoscopy every 5 years; OR Colonoscopy every 10 years; OR CT Colonography every 5 years.
  • Endometrial Cancer:
  • Inform menopausal women regarding clinical signs and risks; advise immediate reporting of unexpected post-menopausal uterine bleeding or spotting to a clinician.
  • Lung Cancer:
  • Adults 50–80 years: Annual Low-Dose Helical CT (LDCT) scan for individuals with a $≥ 20\text{ pack-year}$ smoking history who currently smoke or have quit within the past 15 years.
  • Calculation Example: 1 pack/day for 20 years = 20 pack-years; 0.5 pack/day for 40 years = 20 pack-years.
  • Prostate Cancer:
  • Men 50+ (or age 45 for African American men and men with a first-degree relative diagnosed with prostate cancer before age 65): Shared decision-making regarding Prostate-Specific Antigen (PSA) testing with or without Digital Rectal Examination (DRE) for men with a $≥ 10\text{ year}$ life expectancy.

• Comparison of Society Guidelines for Low-Dose CT Lung Screening:

Staging, Grading, and Diagnostic Modalities

• TNM Staging System Components:

  • Primary Tumor (T): Refers to size, depth, and extent of direct physiological invasion of the primary tumor site (graded numerically from $T_0$ to $T_4$; $T_{is}$ designates carcinoma in situ).
  • Regional Lymph Nodes (N): Assesses absence, presence, or anatomical extent of regional nodal metastases (graded numerically from $N_0$ to $N_3$).
  • Distant Metastasis (M): Assesses absence or presence of systemic distant metastatic spread ($M_0$ = no distant spread; $M_1$ = distant metastasis identified).
  • Overall Stage Grouping: TNM numbers translate into overall clinical stages: Stage I, II, III, or IV.

• Invariance of Staging over Time:

  • A patient's cancer is always formally designated by the stage determined at original diagnosis. If a Stage II cancer recurs later in a distant site, it is documented as "Stage II breast cancer with distant recurrence," not transformed to primary Stage IV.

• Staging Prefixes and Special Systems:

  • c: Clinical staging (based on physical exam, imaging, biopsies prior to surgery; e.g., cT1pN2).
  • p: Pathological staging (determined by microscopic histological analysis of surgical resection specimens).
  • yc: Post-therapy clinical staging (assessed following neoadjuvant chemo/radiation).
  • rp: Restaging pathological evaluation following treatment recurrence.
  • Special Staging Systems: Ann Arbor System (used for Hodgkin and Non-Hodgkin Lymphomas), Rai System (used for Chronic Lymphocytic Leukemia - CLL). Leukemias and primary CNS tumors do not utilize the TNM system.

• Standard Breast Cancer Staging Criteria (AJCC 7th Edition):

  • Stage IA: Tumor $≤ 20\,\text{mm}$, Nodes None ($N_0$), Metastasis None ($M_0$).
  • Stage IB: Tumor $≤ 20\,\text{mm}$, Nodal Micrometastases ($>0.2\,\text{mm}\text{ to }<2.0\,\text{mm}$), $M_0$.
  • Stage IIA: Tumor $≤ 20\,\text{mm}$ with $N_1$, or $>20\,\text{mm}\text{ to }≤ 50\,\text{mm}$ with $N_0$.
  • Stage IIB: Tumor $>20\,\text{mm}\text{ to }≤ 50\,\text{mm}$ with $N_1$, or $>50\,\text{mm}$ with $N_0$.
  • Stage IIIA: Tumor $≤ 50\,\text{mm}$ with $N_2$, or $>50\,\text{mm}$ with $N_1/N_2$.
  • Stage IIIB: Extension to chest wall and/or skin, $N_0≢N_2$, $M_0$.
  • Stage IIIC: Any size primary tumor, $N_3$, $M_0$.
  • Stage IV: Any size tumor, Any node involvement, Detectable distant metastasis ($M_1$).

• Standard Lung Cancer Staging Criteria (TNM):
  • Stage IA: $T_1$ ($≤ 3\,\text{cm}$ surrounded by lung/pleura, no proximal main bronchus involvement), $N_0$, $M_0$.
  • Stage IB: $T_2$ ($>3\,\text{cm}$, main bronchus $≥ 2\,\text{cm}$ distal to carina, invades visceral pleura, lobar atelectasis), $N_0$, $M_0$.
  • Stage IIA: $T_1$, $N_1$ (ipsilateral peribronchial/hilar nodes), $M_0$.
  • Stage IIB: $T_2 N_1 M_0$, or $T_3$ (invades chest wall, diaphragm, pericardium, or main bronchus $<2\,\text{cm}$ to carina) $N_0 M_0$.
  • Stage IIIA: $T_1≢T_3$ with $N_2$ (ipsilateral mediastinal or subcarinal nodes), $M_0$.
  • Stage IIIB: Any $T$ with $N_3$ (contralateral mediastinal/hilar or supraclavicular nodes), $M_0$; or $T_4$ (invades heart, great vessels, trachea, esophagus, spine, carina) Any $N M_0$.
  • Stage IV: Any $T$, Any $N$, $M_1$ (distant metastasis present).

• Tumor Histological Grading:

  • Grading evaluates microscopic cellular differentiation (how closely neoplastic tissue resembles parent normal tissue).
  • High Grade: Poorly differentiated or undifferentiated cells; highly aggressive proliferation and clinical behavior.
  • Low Grade: Well-differentiated cells; less aggressive behavior.
  • Standard 1–4 Grading Scale:
  • Grade 1: Well-differentiated; cells look most like normal cells (Low grade).
  • Grade 2: Moderately differentiated; somewhat abnormal cells (Intermediate grade).
  • Grade 3: Poorly differentiated; cells look significantly abnormal (High grade).
  • Grade 4: Anaplastic / Undifferentiated; highly abnormal structure, growing and spreading rapidly (High grade).

• Diagnostic and Imaging Modalities:

  • Laboratory Tests & Serum Tumor Markers:
  • Serum proteins upregulated by specific tumors used to establish presence, measure treatment efficacy, or monitor for recurrence.
  • CEA (Carcinoembryonic Antigen): Identified in 1965 for colorectal adenocarcinoma.
  • PSA (Prostate-Specific Antigen): Screening and monitoring tool for prostate adenocarcinoma.
  • CA-125: Serous ovarian carcinoma.
  • HER2/neu amplification: Drives targeted therapy selection in breast, ovarian, bladder, gastric, and pancreatic cancers.
  • Computed Tomography (CT): Used for diagnosis, anatomical staging, biopsy guidance, radiofrequency ablation planning, virtual colonoscopy, and low-dose lung cancer screening.
  • Positron Emission Tomography (PET): Utilizes radiolabeled glucose—Fluorodeoxyglucose ($^{18}\text{F-FDG}$)—to evaluate metabolic activity in hypermetabolic tumor cells. Performed concurrently with CT (PET/CT).
  • Nuclear & Bone Scans: Injection of radioisotopes to detect focal areas of high bone turnover indicative of osseous metastases.
  • Magnetic Resonance Imaging (MRI): Utilizes magnetic fields avoiding ionizing radiation; offers high resolution for soft tissue, intracranial, spinal, and musculoskeletal tumors.
  • Ultrasound: Uses high-frequency sound waves to differentiate solid vs. cystic fluid masses.
  • Biopsy: Core needle, incisional, or excisional harvest of tissue for histological analysis (gold standard for diagnosis).

• Comparative Diagnostic Radiation Exposures:

Cancer Treatment Modalities and Effects

• Primary Therapeutic Goals:

  • Prolong overall survival, maximize quality of life, and achieve complete disease cure when feasible.
  • Biomarker testing helps tailor targeted therapies, immunotherapies, and clinical trial eligibility.

• Surgical Oncology:

  • Primary treatment for localized, contained solid tumors.
  • Executed as complete surgical resection or surgical debulking (partial excision to enhance efficacy of subsequent chemo/radiation, e.g., high-grade gliomas).
  • Specialized Techniques: Cryosurgery (uses liquid nitrogen to freeze and destroy dysplasia or superficial localized tumors) and Laser Surgery (used for basal cell carcinoma, cervical carcinoma in situ).

• Chemotherapy Principles and Delivery:

  • Pharmacological agents designed to kill or slow rapidly dividing cells across the cell cycle.
  • Neoadjuvant Chemotherapy: Administered before primary surgical or radiation intervention to reduce tumor volume.
  • Adjuvant Chemotherapy: Administered after surgical resection or radiation to eradicate occult micrometastatic disease.
  • Routes of Administration: Oral, Intravenous (IV), Subcutaneous/Intramuscular injections, Intrathecal (into CSF space), Intraperitoneal, Intra-arterial, and Topical.

• Major Classes of Chemotherapeutic Agents:

• Chemotherapy Toxicity Profile:

  • Acute Toxicities: Severe nausea/vomiting, diarrhea, painful mucositis/stomatitis, peripheral neuropathies, hematologic toxicity (pancytopenia/myelosuppression), CNS confusion, hemorrhagic cystitis.
  • Delayed/Long-Term Toxicities: Pulmonary fibrosis/pneumonitis, cardiomyopathy, endocrine failure (infertility, hypothyroidism), secondary treatment-induced malignancies (e.g., acute myeloid leukemia).

• Hormonal (Endocrine) Therapy:

  • Applied to malignancies that depend on systemic hormone signaling for growth.
  • Tamoxifen: Selective Estrogen Receptor Modulator (SERM) that competitively blocks estrogen receptors in breast tissue, preventing hormone-driven cellular proliferation.
  • Anti-Androgens: Suppress adrenal/testicular androgen production or block androgen receptors to slow prostate cancer growth.

• Radiation Therapy (Radiotherapy):
  • Utilizes high-energy ionizing radiation to induce double-strand DNA damage, destroying targeted tumor cells. Every anatomical site has a strict cumulative lifetime dose limit.
  • External Beam Radiation: Delivered via linear accelerators; includes 3D conformal radiation, image-guided radiotherapy (IGRT), and tomotherapy. Uses thermoplastic mesh immobilization masks to ensure precise positioning.

• Internal Radiation (Brachytherapy): Radioisotope seeds or capsules implanted inside or adjacent to the tumor (e.g., prostate, ocular, cervical, head/neck cancers). Renders the patient temporarily radioactive.

• Side Effects Profile:

  • Short-Term: Generalized fatigue, radiation dermatitis (erythema, desquamation, blistering), localized alopecia. Brain: headaches, cerebral edema, nausea. Breast: localized edema/lymphedema. Pelvis: proctitis, enteritis, dysuria.

  • Long-Term: Brain: neurocognitive decline, memory loss, radiation necrosis, seizures. Breast: chronic skin thickening, fibrosis, breast volume asymmetry. Pelvis: irreversible infertility, severe sexual dysfunction, bowel strictures.

  • Stem Cell Transplantation:

• Replaces and restores damaged hematopoietic stem cells following high-dose, bone-marrow-wiping chemotherapy or total body irradiation.

• Frequently deployed in management of Leukemias, Lymphomas, Neuroblastomas, and Multiple Myelomas.

  • Immunotherapy Modalities:

• Immune Checkpoint Inhibitors: Monoclonal antibodies blocking inhibitory pathways (e.g., PD-1, PD-L1, CTLA-4), enabling cytotoxic T cells to attack tumor cells.

• T-Cell Transfer Therapy (CAR-T Cell Therapy): Patient T cells are genetically engineered ex vivo with Chimeric Antigen Receptors to target specific surface markers on cancer cells.

• Monoclonal Antibodies: Synthetic antibodies designed to target specific surface antigens, flagging cancer cells for immune destruction.

• Treatment Vaccines: Vaccines designed to elicit immune responses against tumor-specific antigens.

• Immune System Modulators: Cytokines (e.g., Interleukin-2, Interferon-alpha) that boost systemic immune responsiveness.

  • Phases of Clinical Trials in Oncology:

• Pre-Clinical Phase: In vitro cellular assays and in vivo animal model safety/efficacy studies.

• Phase 1: Initial human trials assessing safety, maximum tolerated dose (MTD), pharmacokinetics, and toxicity profiles ($15\text{--}30$ subjects).

• Phase 2: Evaluates clinical efficacy against target cancer types and monitors side effects ($<100$ subjects).

• Phase 3: Large randomized controlled trials comparing new interventions against the current standard of care; may utilize placebos ($100\text{s--}1000\text{s}$ subjects).

  • Palliative Care Principles:

• Focuses on treating or preventing disease symptoms, side effects, and associated psychological, social, or spiritual distress as early as possible.

• Can be integrated at any stage of treatment alongside curative therapies; distinct from end-of-life hospice care.